Examining NHD vs QHD in the GCM THOR with non-grey radiative transfer for the hot Jupiter regime

TL;DR

This study compares the effects of different dynamical equations in GCMs on hot Jupiter atmospheres, revealing significant differences in climate states depending on the chosen equations and planetary parameters.

Contribution

It introduces a comparison between NHD and QHD dynamical equations in GCM THOR for hot Jupiters using a non-grey radiative transfer scheme, highlighting the impact of equation choice.

Findings

Differences in climate states depend on gravity, rotation, and irradiation.

Divergent behaviors of GCM approximations are observed for non-Earth planets.

Climate diversity in hot Jupiters is influenced by dynamical equation selection.

Abstract

Global circulation models (GCMs) play an important role in contemporary investigations of exoplanet atmospheres. Different GCMs evolve various sets of dynamical equations which can result in obtaining different atmospheric properties between models. In this study, we investigate the effect of different dynamical equation sets on the atmospheres of hot Jupiter exoplanets. We compare GCM simulations using the quasi-primitive dynamical equations (QHD) and the deep Navier-Stokes equations (NHD) in the GCM THOR. We utilise a two-stream non-grey "picket-fence" scheme to increase the realism of the radiative transfer calculations. We perform GCM simulations covering a wide parameter range grid of system parameters in the population of exoplanets. Our results show significant differences between simulations with the NHD and QHD equation sets at lower gravity, higher rotation rates or at higher irradiation temperatures. The chosen parameter range shows the relevance of choosing dynamical equation sets dependent on system and planetary properties. Our results show the climate states of hot Jupiters seem to be very diverse, where exceptions to prograde superrotation can often occur. Overall, our study shows the evolution of different climate states which arise just due to different selections of Navier-Stokes equations and approximations. We show the divergent behaviour of approximations used in GCMs for Earth, but applied for non Earth-like planets.